Exam 2 Flashcards
A heritable feature that varies among individuals, such as flower color
character
Variant for a character such as purple or white color for flowers
trait
Two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
law of segregation
Organism that has a pair of identical alleles for a chacter
homozygous
Has two different alleles for a gene
heterozygous
Organism’s appearance or observable traits
phenotype
Organism’s genetic makeup
genotype
Crossing two heterozygous parents to follow a single chacter (such as flower color)
monohybrid cross
Crossing individual heterozygous for two chacters being followed (i.e. YyRr)
dihybrid cross
Each pair of alleles segregates independently of each other pair of alleles during gamete formation
law of independent assortment
Phenotypes of the heterozygote and the dominant homozygote are indistinguishable
complete dominance
Neither allele is completely dominant and the F1 hybrids have a phenotype somewhere between those of the two parental varieties
incomplete dominance
Two alleles each affect the phenotype in separate, distinguishable ways
codominance
Genes that have multiple phenotypic effects
pleiotropy
The phenotypic expression of a gene at one locus alters that of a gene at a second locust
epistasis
Ex: A second gene determines whether or not pigment will be deposited in the hair. If lab is homozygous recessive for the second locust (ee) coat will be yellow regardless
epistasis
Ex: Alleles that are responsible for the multiple symptoms associated with certain hereditary diseases, such as cystic fibrosis and sickle-cell disease
pleiotropy
An additive effect of two or more genes on a single phenotypic character (the converse of pleiotropy)
polygenic inheritance
Ex: Skin pigmentation in humans controlled by at least three separately inherited genes
polygenic inheritance
A heritable feature that varies continuously over a range rather than in an either-or fashion
quantitative character
Ex: All F1 offspring had red eyes so the mutant white-eye trait must be recessive to the wild-type red-eye trait. Since only expressed in F2 Males, Morgan deduced eye-color gene located on X chromosome
Thomas’s Fruit Fly experiement
Genes located on either sex chromosome
Sex-Linked genes
The inactive X in each cell of a female condenses into a compact object
Barr body
If either of the aberant gametes unites with a normal one at fertilization, the zygote will also have an abnormal number of a particular chromosome
aneuploidy
Ex: Down syndrome is an example of trisomy, and Turner’s syndrome
aneuploidy
An ordered list of the genetic loci along a particular chromosome (Alfred H. Sturtevant)
genetic map
The members of a pair of homologous chromosomes do not move apart properly during meiosis I
nondisjunction
Sister chromatids fail to separate during meiosis II
nondisjunction
One gamete receives two of the same type of chromosomes and another gamete receives no copy
nondisjunction
Chromosomal fragment is lost. The affected chromosome is then missing certain genes.
deletion
A “deleted” fragment may become attached as an extra segment to a sister chromatid
duplication